1. Field of the Invention
This invention relates to a camera body, an optical accessory or a camera system.
2. Description of the Related Art:
Camera systems of the kind having optical accessories such as an interchangeable lens, an intermediate tube, various converters, etc. detachably mounted on a camera body by a bayonet mount device have been known.
The application of electronics to camera systems has advanced during recent years. As a result, communication and power supply arrangement have become necessary between the camera body and the optical accessory. To meet this requirement, camera systems of varied kinds have been proposed. They have electric connection terminals such as contact pins or the like arranged on both the optical accessory and the camera body. The arrangement is such that: The terminals arranged on both sides come into contact with each other when the optical accessory is mounted on the camera body by rotating the mounts of both sides relative to each other. With the optical accessory mounted, the camera body supplies electric energy to the optical accessory and reads the content of a ROM included in the optical accessory.
An arrangement to minimize wear due to sliding contact between the electric connection terminals of the camera body and those of the optical accessory has been proposed as disclosed in U.S. patent applications Ser. No. 016,653 filed on Feb. 19, 1987 and Ser. No. 136,976 filed on Dec. 23, 1987. In accordance with the proposed arrangement, the electric connection terminals of the two are provided with stepped differences in level which are formed to lessen the number of tires of the sliding contact for minimal wear in the direction of their contact when the two mounts are rotated for mounting.
In the case of the above arrangement, two connection terminals (a high potential terminal and a grounding terminal) and a plurality of connection terminals for communication are arranged stepwise to have different heights in the contact direction As a result, two connection terminals for power supply are adjacently disposed. The arrangement presents no problem as long as the power supply is effected from the camera body to the optical accessory after detection of completion of the mounting action of the two mounts. However, in cases where the electric energy is arranged to be constantly supplied from the camera body side, the two adjacent power supply terminals might be short-circuited if, for example, a metal piece is inadvertently brought near to them. In such a case, circuits disposed on the side of the camera body might be broken.